package util;

/**
 * The Bouncy Castle License
 *
 * Copyright (c) 2000 The Legion Of The Bouncy Castle (http://www.bouncycastle.org)
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy of this software 
 * and associated documentation files (the "Software"), to deal in the Software without restriction, 
 * including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, 
 * and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so,
 * subject to the following conditions:
 * 
 * The above copyright notice and this permission notice shall be included in all copies or substantial
 * portions of the Software.
 * 
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED,
 * INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR
 * PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
 * LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
 * OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
 * DEALINGS IN THE SOFTWARE.
 */


public final class Base64
{
  private static final byte[] encodingTable =
  { (byte)'A', (byte)'B', (byte)'C', (byte)'D', (byte)'E', (byte)'F', (byte)'G',
    (byte)'H', (byte)'I', (byte)'J', (byte)'K', (byte)'L', (byte)'M', (byte)'N',
    (byte)'O', (byte)'P', (byte)'Q', (byte)'R', (byte)'S', (byte)'T', (byte)'U',
    (byte)'V', (byte)'W', (byte)'X', (byte)'Y', (byte)'Z',
    (byte)'a', (byte)'b', (byte)'c', (byte)'d', (byte)'e', (byte)'f', (byte)'g',
    (byte)'h', (byte)'i', (byte)'j', (byte)'k', (byte)'l', (byte)'m', (byte)'n',
    (byte)'o', (byte)'p', (byte)'q', (byte)'r', (byte)'s', (byte)'t', (byte)'u',
    (byte)'v', (byte)'w', (byte)'x', (byte)'y', (byte)'z',
    (byte)'0', (byte)'1', (byte)'2', (byte)'3', (byte)'4', (byte)'5', (byte)'6',
    (byte)'7', (byte)'8', (byte)'9',
    (byte)'+', (byte)'/'
  };

  private static final byte[] decodingTable;
  static
  { decodingTable = new byte[128];
    for(int i='A';i<='Z';i++) { decodingTable[i]=(byte)(i-'A'); }
    for(int i='a';i<='z';i++) { decodingTable[i]=(byte)(i-'a'+26); }
    for(int i='0';i<='9';i++) { decodingTable[i]=(byte)(i-'0'+52); }
    decodingTable['+']=62;
    decodingTable['/']=63;
  }

  /**
  * encode the input data producing a base 64 encoded byte array.
  *
  * @return a byte array containing the base 64 encoded data.
  */
  public final static byte[] encode(byte[] data)
  { byte[] bytes;
    int modulus = data.length % 3;
    if (modulus == 0)
         bytes = new byte[4 * data.length / 3];
    else bytes = new byte[4 * ((data.length / 3) + 1)];

    int dataLength = (data.length - modulus);
    int a1, a2, a3;
    for (int i = 0, j = 0; i < dataLength; i += 3, j += 4)
    { a1 = data[i] & 0xff;
      a2 = data[i + 1] & 0xff;
      a3 = data[i + 2] & 0xff;
      bytes[j] = encodingTable[(a1 >>> 2) & 0x3f];
      bytes[j + 1] = encodingTable[((a1 << 4) | (a2 >>> 4)) & 0x3f];
      bytes[j + 2] = encodingTable[((a2 << 2) | (a3 >>> 6)) & 0x3f];
      bytes[j + 3] = encodingTable[a3 & 0x3f];
    }

    // process the tail end.
    int b1, b2, b3;
    int d1, d2;

    switch(modulus)
    { case 0: break; /* nothing left to do */
      case 1: d1 = data[data.length - 1] & 0xff;
              b1 = (d1 >>> 2) & 0x3f;
              b2 = (d1 << 4) & 0x3f;
              bytes[bytes.length - 4] = encodingTable[b1];
              bytes[bytes.length - 3] = encodingTable[b2];
              bytes[bytes.length - 2] = (byte)'=';
              bytes[bytes.length - 1] = (byte)'=';
              break;
      case 2: d1 = data[data.length - 2] & 0xff;
              d2 = data[data.length - 1] & 0xff;
              b1 = (d1 >>> 2) & 0x3f;
              b2 = ((d1 << 4) | (d2 >>> 4)) & 0x3f;
              b3 = (d2 << 2) & 0x3f;
              bytes[bytes.length - 4] = encodingTable[b1];
              bytes[bytes.length - 3] = encodingTable[b2];
              bytes[bytes.length - 2] = encodingTable[b3];
              bytes[bytes.length - 1] = (byte)'=';
              break;
    }
    return bytes;
  }
  

  /**
   * decode the base 64 encoded input data.
   *
   * @return a byte array representing the decoded data.
   */
  public final static byte[] decode(byte[]data)
  { byte[]bytes;
    byte b1, b2, b3, b4;
    if(data[data.length-2] == '=')
         bytes=new byte[(((data.length / 4) - 1) * 3) + 1];
    else if(data[data.length-1] == '=')
         bytes=new byte[(((data.length / 4) - 1) * 3) + 2];
    else bytes=new byte[((data.length / 4) * 3)];

    for(int i = 0, j = 0; i < data.length - 4; i += 4, j += 3)
    { b1 = decodingTable[data[i]];
      b2 = decodingTable[data[i + 1]];
      b3 = decodingTable[data[i + 2]];
      b4 = decodingTable[data[i + 3]];

      bytes[j] = (byte)((b1 << 2) | (b2 >> 4));
      bytes[j + 1] = (byte)((b2 << 4) | (b3 >> 2));
      bytes[j + 2] = (byte)((b3 << 6) | b4);
    }

    if(data[data.length - 2] == '=')
    { b1 = decodingTable[data[data.length - 4]];
      b2 = decodingTable[data[data.length - 3]];

      bytes[bytes.length - 1] = (byte)((b1 << 2) | (b2 >> 4));
    }
    else if(data[data.length - 1] == '=')
    { b1 = decodingTable[data[data.length - 4]];
      b2 = decodingTable[data[data.length - 3]];
      b3 = decodingTable[data[data.length - 2]];

      bytes[bytes.length - 2] = (byte)((b1 << 2) | (b2 >> 4));
      bytes[bytes.length - 1] = (byte)((b2 << 4) | (b3 >> 2));
    }
    else
    { b1 = decodingTable[data[data.length - 4]];
      b2 = decodingTable[data[data.length - 3]];
      b3 = decodingTable[data[data.length - 2]];
      b4 = decodingTable[data[data.length - 1]];

      bytes[bytes.length - 3] = (byte)((b1 << 2) | (b2 >> 4));
      bytes[bytes.length - 2] = (byte)((b2 << 4) | (b3 >> 2));
      bytes[bytes.length - 1] = (byte)((b3 << 6) | b4);
    }
    return bytes;
  }

}